Process of bleaching vegetable fibers



the equimolecular v UNITED STATES PATE NT OFFICE.

GEORGE TAYLOR, OF HOLYOKE, MASSACHUSETTS, ASSIGNOR TO AMERICAN I WRITING PAPER COMPANY, OFQEOLYOKE, MASSACHUSETTS, A CORPORA- TION OF NEW JERSEY.

PROCESS OF BLEACIHING VEGETABLE FIBERS.

No Drawing.

To all whom it may concern: 7

Be it known that I, GEORGE G. TAYLOR, a citizen of the United States, residing at Holyoke, in the county of Hampden and State of Massachusetts, have invented certain new and useful Improvements in Processes of Bleaching-Vegetable Fibers, of which the following is a specification.

This invention relates to the art of bleaching vegetable fibers, and comprises a novel process whereby such fibers may be quickly bleached without injurious efiect due to the bleaching agent.

It has long been recognized that hypochlorous acid, owing to the comparative readiness with which it parts with oxygen, is a much more energetic and rapid bleaching agent than any of its salts. ingly it is customary,

in employing hypochlorites as bleaching agents, to introduce into the bath at some stage of the operation an acid or acid salt in order to liberate free hypochlorous acid.

In the textile industry this is accomplished by passing the cloth saturated with the hypochlorite bleaching solutions into a bath of dilute acid. -The paper maker; who is obliged to bleach his material in the form of pulp, adds acid or an acid reacting salt to the washing engine, or to such other apparatus as may be employed for bleaching, before the bleach liquor isexhausted. The acids most commonly used in both industries are sulfuric and acetic acids,.while sulfate of aluminum is the salt usually employed.

The disadvantage of the addition of any of the above materials as now commonly emf ployed consists first in the fact that when hypochlorous acid gives up its oxygen in .the course of the bleaching operation, hydrochloric acid is formed; and hydrochloric acid even in very dilute solution has an injurious action upon cellulose fibers; and second, in the fact that .the addition of an excess of any of these materials decomposes the hypochlorite with evolution of chlorin,

which is not a primary bleaching agent.

According to the present invention. these difficulties are overcome by adding to the bleachin bath, comprising any of the salts of hypoclilorous acid, boric acid in less than proportion to the hypo- The boric acid liberates chlorite present.

from a. portion of the hypochlorous acid Specification of Letters Patent.

Accord- ,chlorite remains.

Patented June 14, 1921.

Application filed December 18,1920. Serial No. 431,794.

hypochlorite, a corresponding quantity of borate being of course formed; the latter salt is however at once decomposed by the hydrochloric acid resulting from the decomposition of the hypochlorous acid, whereby boric acid is again set free, and the cycle repeated until the whole of the hypochlorite has been utilized in the form of free hypochlorous acid.

Assuming sodium hypochlorite to be the bleaching agent employed, and a small pro portion of boric acid to be added during the bleaching operation, the cycle of ensuing reactions may be represented as follows:

Sodium Bone Sodium Hypochlo- Water. hypochlorite. acid. borate. rous acid.

II. 2HOC1 2H0! O: L Hypo- Hydro- Oxygen. chlorous chloric acid. acid.

III. H01 NaBO- H O NaCl H3BO Hydto- Sodium Water. Sodium Boric chlo'ic borate. chlorid. acid.

aci

The regenerated boric acid will go through the cycle of reactions as long as any hypo- In the case of calcium hypochlorite the reactions will be similar, viz: I. CaSOCl), 2H3B0; Ca(BO2)2 2HOC1 2H,0

Ca cium Boric Calcium Hypo- Water.

hypoacid. borate. chloroul ch orite. acid, II. 2HOC1-) 2H0! 0 Hypo- Hydro- Oxygen. chlorous chloric acid. acid. III. 2H0] Ca(B0g)g ZHQO 09.01, 2H.:B Os

Hydro- Calcium Water. Calcium Bone chlgic borate. chlorid. acid.

aci

, In either case it will be noted that the boric acid is regenerated, and therefore' that a small amount of it will be suflicient to liberate all the hypochlorous acid contained in a large amount of bleaching powder or of sodium hypochlorite. In actual practice; I prefer to use about on pound of bone acld for each 100 pounds of paper stock,-but my invention is of course not llmited to this approximate proportion.

I claim:

Process of bleaching vegetable fibers, cornprising subjecting the fiber to a hypochlorite .mpresence of free boric acid, the latter in less than the equimolecular proportion to the hypochlorite.

whereof I'aflix my slgnature.

In testimony GEORGE G. TA R. p 

